1. Field of Invention
The invention relates to near field communications (NFC), and more specifically to reducing emission from a NFC capable device.
2. Related Art
Near field communications (NFC) requires that NFC devices to be present within a relatively small distance from one another so that their corresponding magnetic fields can exchange information. Ranges of up to several centimeters (generally a maximum of 1 meter) are common for NFC devices. Typically, a first NFC device transmits or generates a magnetic field modulated with the information, such as the credit information or the ticket fare information. This magnetic field inductively couples onto a second NFC device that is proximate to the first NFC device. The second NFC device may respond to the first NFC device by transmitting or generating its own modulated magnetic field and inductively coupling this magnetic field to the first NFC device. There are several standards in existence which set out certain communication protocols and functional requirements for NFC and other communications using the near field, such as ISO/IEC 14443, ISO 15693, ISO/IEC 18092 and ISO/IEC 21481.
A NFC communicator is a type of NFC device that is capable of operating in an initiator mode to initiate a communication with another NFC enabled device and in a target mode to respond to the initiation of a communication by another NFC enabled device. The term “NFC enabled device” includes not only the NFC communicator but also other initiator NFC enable devices, such as a RFID transceiver or reader that are capable of initiating a near field RF communication and/or a RFID transponder or tag that are capable of responding to initiation of a NFC by another NFC enabled device to provide some examples. Hence, the NFC communicator can act as both a RFID transceiver and a RFID transponder and are able to communicate with other NFC communicators, RFID transceivers and RFID transponders.
NFC devices are being integrated into mobile devices, such as mobile telephones to provide an example, to facilitate the use of these mobile devices in conducting daily transactions. For example, instead of carrying numerous credit cards, the credit information provided by these credit cards could be stored onto a NFC device. The NFC device is simply tapped to a credit card terminal to relay the credit information to it to complete a transaction. As another example, a ticketing writing system, such as those used in bus and train terminals, may simply write ticket fare information onto the NFC device instead of providing a ticket to a passenger. The passenger simply taps the NFC device to a reader to ride the bus or the train without the use of a paper ticket.
Commonly, the mobile devices include a high frequency receiver and transmitter for long range communications over large distances. When the NFC device is integrated into these mobile devices, it is advantageous to reduce unwanted emissions from the NFC device in frequency bands employed by the mobile devices. Thus, there is a need to reduce unwanted emissions from the NFC device when it is integrated into a host device. Further aspects and advantages of the invention will become apparent from the detailed description that follows.
The invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.